The miner has its eyes on 450sq km of the Chatham Rise, a flat-topped ridge that runs 700km beneath the sea from Canterbury to the Chathams. Warm ocean currents from the tropics meet cold sub-Antarctic waters above the ridge, making the area one of New Zealand's most productive fishing grounds, as well as a key element in the Chathams economy.
The process of extracting phosphate lumps from the sea floor is far from straightforward. Besides the technical challenges it faces, Chatham Rock, which has ploughed millions into the project, still needs two vital consents before its partners in the venture can start work.
It is striking formidable resistance in New Zealand and wariness on the Chathams, where Mayor Preece says the islands' dependence on the sea has made the community apprehensive about new technology in their maritime backyard.
The latest critic to weigh in against the scheme was Green Party MP Gareth Hughes, who this week argued that the law covering the deep-sea riches was inconsistent.
"I think it makes a mockery of our marine protections to allow literally vacuuming up the seabed in a marine protected area," Hughes said.
The MP was referring to the status of the Rise as a Bethnic Protection Area, which makes it off-limits to bottom dredging but not, under existing law, to seabed mining.
Chatham Rock managing director Chris Castle replied in an open letter: "We're astonished you have formed such a negative opinion about our project given the compelling potential environmental and economic benefits it offers and its minimal environmental impacts."
In a nutshell, Castle's remarks identified where this conflict is likely to be settled - the environmental battlefront.
Castle, an accountant who cut his teeth in the hard-nosed corporate world of Brierley Investments, insists his company wouldn't contemplate the new undersea frontier if the work caused "more than very minor environmental impacts".
He says 85 per cent of the material it wants to lift from the Chatham Rise would be placed back from where it came. "Modelling indicates the material will not be widely dispersed and the sediment that doesn't immediately settle will rapidly dilute to insignificant levels."
He says more than 30 expert reports commissioned by Chatham Rock for a draft environmental impact assessment had not identified any long-term impacts on fish habitats - a key claim because of the fisheries interests.
Castle insists that any impacts would be confined to the areas mined, and be "short-term, reversible and of low environmental risk".
Responds George Clement of the Deepwater Group, a fisheries industry lobby: "We just don't know."
Clement calls the project "potentially catastrophic" for the marine environment and fears that sediment plumes carried on sea floor currents will drift over long distances, smothering corals and sponges that act as nurseries for valuable fish species. "We need to be reassured that this isn't so," he says, and uses the term "strip mining" to describe the scheme.
Argues Clement: "Our seafood is here forever, long after the phosphate has gone."
Chatham Rock and the Deepwater Group also have exchanged barbs over their technologies. Castle, the mining advocate, says his project has to jump through the hoops to get a mining licence and a marine consent, the underwater equivalent of a resource consent.
"These cost millions of dollars, require years of research, consultation and official process and involve full public scrutiny."
Bottom trawling, he argues, needs no consents and each year disturbs or destroys creatures more than 50,000 sq km of New Zealand's seabed. He believes the fishing industry is making a rod for its own back by reminding those observing the controversy just how destructive of the sea floor its methods can be.
Clement uses his own analogy to compare seabed mining and bottom trawling. "It's like [comparing] a bulldozer in a national park removing all life including topsoil down to half a metre with a farmer running over his paddock with a roller. "
He calls the Chatham Rise "our CBD" and says he could imagine the uproar if a miner wanted an open-cast dig across the Auckland isthmus.
Responds Castle: "We're not losing any sleep over the nonsense coming out of the Deepwater Group ... they regard it as their sandpit and don't want us there at all. They've just decided they don't want us on their patch."
Phosphate nodules formed by a complex interplay of ancient erosion, ocean chemistry and currents have lain undisturbed on the Chatham Rise for millions of years. Discovered in the 1950s, the deposits caused flutters of excitement 30 years ago when the Government and some big corporates took a close look at exploiting the resource. Costs made the work prohibitive then, but a shift in phosphate prices and new mining technology has put the nodules within tantalising reach.
Three years ago Castle, managing director of Chatham Rock, secured an exploration licence covering 4726sq km of the Chatham Rise. The licence - issued on a first come, first served basis - remains the company's most valuable asset, though Castle says the knowledge it has built up about the sea floor resource and the means to extract it is valuable intellectual property.
Castle is chuffed his company - he calls it a "tinpot" set-up from Golden Bay - is still afloat when swags of miners have gone to the wall. He runs the show from an office in Wellington, where he and his partner, Linda Sanders, spend the working week before flying back to their home at Onekaka, a tiny settlement near Takaka that in the 1920s supported an iron ore industry. Sanders, who writes an investment column for the Listener, chairs Chatham Rock's board and is charge of corporate affairs. Its team includes a geologist, scientist and an environmental consultant.
Castle has had the mining bug for years, ever since he worked in the minerals arm of corporate raider Brierley. He created Charter Corp, which collapsed in 1988, and went on to set up mining investor Widespread Portfolios, now called Aorere.
Financing the Chatham project had been tough, recalled Castle, with capital markets going into a tailspin after the global financial crisis. A breakthrough came last year when Subsea Investments, an American private equity firm, took a stake in the company, before Dutch multinational Royal Boskalis got on board. Odyssey Marine, an American firm specialising in recovering shipwrecks with submersible robot craft, also has a share in Chatham Rock.
Boskalis took its slice in return for the early mining work. It is also designing the technology to recover the fertiliser and, if the consents come through, would adapt one of its giant vessels for the mid-ocean work.
The big dredging company would need to modify one of its 200m long vessels to harvest the phosphate. Each trip would cover a 12-day cycle. Three days would be set aside to fill its holds 50,000 tonnes of phosphate, with a further nine days to unload the cargo and return to the Chatham Rise.
Company estimates say the resource could be mined for at least 15 years, deliver a $900 million benefit to New Zealand, and offset the need to import phosphate from Morocco.
Given the forbidding environment where the ship must operate, Chatham Rock expects that wild weather could sometimes disrupt work. But the miner still expects to shift 1.5 million tonnes of phosphate each year from the sea floor to an as yet undetermined New Zealand port.
Castle admits the project has taken longer than his company had anticipated. In public statements, Chatham Rock was confident of getting its mining licence this year, with work starting in 2015. That date has been pushed back to 2016. Castle says his company has received a "letter of comfort" from NZ Petroleum and Minerals, the Economic Development Ministry agency which manages the country's oil, gas, mineral and coal resources, that they are dealing with the application as a matter of priority.
He doesn't expect further hiccups. "We expect to get both permits by mid-2014. Then's it's two years to modify the ship. The day we get those consents this company is worth $500 million." Its present market capitalisation is $46 million.
Castle has been active building support for the project. He's taken a team to the Chathams, suggesting the mining could be a "game-changer" for the windswept territory. As part of its pitch, the company has mentioned delivering a load of phosphate, suggested service jobs could be created and raised the possibility of stationing a helicopter for emergencies on the island.
In Wellington, Castle acknowledges he is "frequent visitor" to the Beehive and says he has worked hard to promote his scheme to ministers and officials. There remains some way to travel. No extraction at this depth has been tried before. Furthermore, the matter of marine consents is new bureaucratic territory. Just this week authorities in faraway Namibia put the brakes on an undersea plan to mine phosphate nodules. Reports said an 18-month moratorium had been slapped on offshore mining activities because of environmental uncertainties.
"In the end it's going to come down to the science," asserts Castle. He says the marine consent hearing by the Environmental Protection Authority - the first under a new law - will be persuaded by the facts, not signatures on a petition or lobbying by the fishing industry.
Over on the Chathams - the land at the end of the weather forecast - Mayor Preece says islanders view the plan to mine with a mixture of excitement and concern. "Fishing is our lifeblood. It's been the case since the days of whaling and sealing, so we're concerned that the industry we have now is not damaged in any way."
A farmer, Preece says Chatham Rock's suggestion of a shipment fertiliser went down well, given its prohibitive cost. "If it goes ahead safely we'd be keen to see some of the royalties come our way. We just don't want to get ripped off."
Economic feed
• Each year New Zealand uses about one million tonnes of phosphate, worth $300 million, to encourage pasture growth to drive its land-based economy.
• The fertiliser is made from rock phosphate from Morocco. There is, however, a catch - the north African phosphate contains relatively high levels of cadmium, a toxic element found naturally in soils. Chronic exposure to the heavy metal has been linked to kidney failure and brittle bones.
• Cadmium levels in New Zealand soils and farm animals are monitored by the Ministry for Primary Industries as part of a programme managed by the Cadmium Working Group, which includes state agencies, primary sector groups and the fertiliser industry.
• MPI says evidence to date indicates cadmium in soils poses no immediate concern, though export bans have been imposed on kidneys from sheep and cattle over 30 months. New Zealand fertiliser companies have a voluntary limit of 280 parts per million of cadmium for manufactured superphosphate.
• Chatham Rock Phosphate says tests on samples collected from 11 locations on the Chatham Rise showed an average of 2.2 parts per million. The lowest value was 1.3ppm, with a high of 5.3ppm. It argues the lower level is a factor in its favour in its bid to secure consents to mine the seabed.
